In the production of alcohol from grain for use in making what is termed "Gasohol", a mixture of gasoline and alcohol, it is necessary to reduce the moisture content of alcohol before mixing with gasoline to essentially zero, which is equivalent to a proof of 200, since any water in the alcohol reduces the effectiveness of the gasoline. The alcohol being liquid may be produced by a mash fermented from grain or other suitable materials. In the usual stills which evaporate alcohol produced from mash, the alcohol still contains an undesirable amount of water, the proof thereof normally approaching 190 or 5% water.
A molecular sieve material, such as Type 3A molecular sieve manufactured by Union Carbide Corporation and also by W. R. Grace and Company is particularly useful in removing the moisture or water and producing a 200 proof alcohol. Such molecular sieve material is available in the form of granules and may be placed in a container through which the 190 proof alcohol is passed, so that the molecular sieve material absorbs the water. For a production operation, in which down time is of the essence, the molecular sieve material must be regenerated whenever it becomes essentially saturated with water, and therefore fails to produce the desired proof of alcohol. Such molecular sieve material may be regenerated by heat, but it requires an undue amount of time to heat any substantial size of bed of such material. Thus, the time required for regeneration of a substantial size bed may approach the time during which the bed is operative to produce the desired results. This means that there is no production of the desired alcohol for approximately 50% of the time.
It has been proposed to revivify carbonaceous absorbents such as bone char, as in U.S. Pat. No. 2,851,428 by passing the char downwardly through parallel tubes surrounded by a heating medium, preferably heated gases. Also, U.S. Pat. No. 2,222,304 discloses a method and apparatus for catalytic reaction in which the catalytic reaction is controlled by circulating a temperature controlled heat exchange medium in heat exchange relationship with the material in a contact bed which has a relatively greater length in proportion to its transverse dimension by passing the heat exchange medium through tubes provided with outwardly extending fins or plates. However, the distance between the tubes is much greater than would permit an adequate and sufficiently fast transfer of heat for regeneration of a molecular sieve material. Of course, the catalyst, itself, is regenerated by passing in an oxidizing medium through the bed, while maintaining circulation of the heat transfer medium. Neither of the foregoing appear to suggest a satisfactory solution to the problem of producing a fast enough heating of a molecular sieve material for regeneration thereof, accompanied by a relatively fast cooling thereof to place the material at the temperature suitable for further extraction of water or moisture from alcohol. Since the removal of water or moisture from alcohol by a molecular sieve material is exothermic and the material tends to become heated during reaction, it is necessary that the molecular sieve material be returned to a lower temperature, such as 200.degree. F., prior to initiating further removal of moisture.